Tissue diagnostics is becoming more important to patient care and requires ever more automation to meet the growing demand for throughput. Automated immunostaining technology is widely used in most IHC laboratories. The instruments are designed to mimic manual immunostaining process, including the critical steps such as antigen retrieval, antibody and solution application, incubation and washing. Different systems have varying degree of flexibility and slides capacity, but their goals are the same: minimize errors and provide high quality staining so consistent interpretation can be drawn from patient samples.
However, despite the provision of engineering control tools in these autostainers, it is not rare to have issues with incorrect dispensing of staining solution and incomplete coverage of patient samples due to air bubble or presence of thick, loose or folded tissue sections, which then creates issues of false negative and non-uniform staining for analysis. See, e.g., Shi, S.-R., Taylor, C. R., Antigen Retrieval Immunohistochemistry Based Research and Diagnostics, 2010, Wiley, Singapore. Furthermore, typical autostainers on the market limit the staining area to about 50 m m long. One manufacturer's coverslip technique limits the staining area to 21×50 mm, Another manufacturer's liquid vortex air mixing protocol covers a 25×50 mm staining area. There is currently no control method to validate that the whole tissue section within these specified staining area are stained equally or completely.
Currently the inadequate staining of tissue on a slide is only identified retrospectively. Many not-so-obvious incidents may have gone unnoticed. HercepTest™ from Dako includes a separate slide containing three pelleted, formalin-fixed, paraffin-embedded human breast cancer cell lines with staining intensity scores of 0, 1+ and 3+, which was included in each staining run as a batch control. However, batch controls cannot identify any staining defects on each individual slide within the batch.
Another previous approach prepares patient sample sections on top of slides which already contain positive or negative tissue or cell controls. Sources of these tissues vary depending on the facility and their staining behavior will differ from batch to batch due to patient variability. As shown in FIG. 1, the prior art provides a tissue sample slide 1 having a planar substrate 2 on which are affixed a tissue sample 3 and a cell control 4. The cell control 4 is in the form of cell pellets affixed to the slide in a region between the sample and one longitudinal end 5 of substrate 2. FIG. 2 depicts another tissue sample slide 1′ of the prior art, sold by Bio-Quick Corporation of Rockville, Md., which includes a 9-dot array of cell controls 4a-i for cancer marker IHC assays (http://www.bio-quick.com/qc-dots%C2%AE-cancer-array-ca-control-slides). Cell controls 4a-i can include positive and negative controls but are each shown to be distinct controls from each other. Although slide 1′ contains cell pellets arrays, it offers similar information as a slide containing a single cell pellet. That is, the cell pellet markers are solely used for calibration of the signals received from the tissue sample being analyzed. Like for slide 1, slide 1′ positions controls 4a-I between the sample and one longitudinal end 5′ of the substrate 2′ and may thus be near or far away from the patients' sample depending on the size of sample and skills of the operator. The location of these controls to a single side of the tissue thus does not provide a reliable indication of whether or not the tissue sample itself was stained completely and uniformly.
The art therefore lacks a slide which uses the controls in a manner to assure a tissue sample has been stained in its entirety, both completely and uniformly.